This proposal is directed towards elucidation of the means by which growth hormone regulates metabolic pathways related to energy metabolism. Although it is the most abundant of the pituitary hormones and clearly influences growth, the essential nature of its effects on responsive tissues remains unknown. Although recent achievements in the production of synthetic growth hormone promise to relieve the shortage which has limited its use therapeutically, the poor understanding of its role in the devlopment of tissues and in the regulation of their metabolism may limit the effectiveness with which it may be administered to patients in the future. A better understanding of the function of this hormone in normal individuals is likely to improve the administration of other drugs, many of which are likely to affect many of the metabolic processes which are regulated by growth hormone as well as by other hormonal and metabolic factors. The specific aims of this proposal are: 1. To isolate and characterize the growth hormone receptors located on the surface of adipose tissue cells. 2. To investigate the possibility that intracellular concentrations of calcium and of metabolic intermediates derived from phospholipids may act as a second messenger. 3. To continue investigations of several of the metabolic targets of growth hormone action and how they are related to one another.